Question

Find energy of each of the photons which
(i) correspond to light of frequency 3× 10¹⁵ Hz.
(ii) have wavelength of 0.50 Å.

Answer 1

(i) Energy (E) of a photon is given by the expression,

E=hv

Where, h = Planck’s constant = 6.626 × 10^–34 Js
ν = frequency of light = 3 × 10¹⁵ Hz
Substituting the values in the given expression of E:
E = (6.626 × 10^–34) (3 × 10¹⁵)
E = 1.988 × 10^–18 J
(ii) Energy (E) of a photon having wavelength (λ) is given by the expression,

E=hc/λ

h = Planck’s constant = 6.626 × 10^–34 Js

c = velocity of light in vacuum = 3 × 10⁸ m/s
Substituting the values in the given expression of E:

E=(6.626*10^-34)(3*10⁸)/0.50*10^-10=3.976*10^-15 J

E=3.98*10^-15 J